Sensor for fluid level - uses electrically heated thermistor with sudden change from high to low resistance at temperature rise

摘要

A level sensor for producing a warning signal if the brake fluid for motor cars drops below a danger level consists of an electrical heating element (22) which is coupled by a heat transmitting connector (27) to a resistor (24). The latter is made of a material which suddenly changes from a high to a low resistance at a certain temperature. The sensor is attached by the fitting (26) to the brake fluid container. The preferred material for the resistor (24) is Ti3O5 which has a transition temperature of 165 deg.C. This eliminates the high temperature rise required by ordinary thermistors and has a desirable self-locking effect once a dropping fluid level has caused it to respond.